Resistance Training Adaptations PDF

Neuromuscular Adaptations Gains in Muscular Fitness 2 After 3 to 6 months of resistance training Learn to more effectively produce force Learn to produce true maximal movement 25 to 100% strength gain Altered neural control Muscle hypertrophy Strength gain pot...

Neuromuscular Adaptations Gains in Muscular Fitness 2 After 3 to 6 months of resistance training Learn to more effectively produce force Learn to produce true maximal movement 25 to 100% strength gain Altered neural control Muscle hypertrophy Strength gain potential higher in young males Higher level of muscle plasticity Responses to Training Stress 3 Selye’s General Adaptation Syndrome What determines whether you end up with adaptation or exhaustion? General Adaptation Syndrome (GAS) Adaptation or Alarm Resistance Exhaustion  General 4 Adaptation Syndrome (Shock / Stress / Overload) Fig. 21.1. Haff et al. 2016. Essentials of Strength… Human Kinetics  Muscle Damage Elicits Adaptations Fig. 22.27. McArdle et al. 2015. Exercise Physiology… LWW Example of Glycogen Supercompensation  Adaptations to Resistance Training Tab. 22.5. McArdle et al. 2015. Exercise Physiology… LWW Adaptations in all elements of Force Gradation 8 Recall that the amount of force generated in a single muscle fiber is dependent upon the # of crossbridges We discussed 5 ways that a person can acutely increase the amount of force generated. Many of the neuromuscular adaptations lead to increased force output because they alter these same 5 factors: 1) Number of motor units recruited 2) Frequency of motor unit discharge 3) Type of motor unit recruited 4) Activation of the stretch reflex) 5) Speed of contraction Fig. 19.7. McArdle et al. 2015. Exercise Physiology… LWW Neural Adaptations  Neural Adaptations 10 Anaerobic training may elicit adaptations along the neuromuscular chain, beginning in the higher brain centers and continuing down to the level of individual muscle fibers. Greater adaptations with high-intensity training Dramatic increases in neural adaptations take place early in the training program. Fig. 22.19. McArdle et al. 2015. Exercise Physiology… LWW 10  Neural Adaptations 11 Central Adaptations Motor cortex activity increases when the level of force developed increases and when new exercises or movements are being learned. Adaptations of Motor Units Maximal strength and power increases of agonist muscles result from an increase in recruitment, rate of firing, synchronization of firing, or a combination of these factors. Only ~70% of muscle tissue can be voluntarily activated by untrained individuals. Fig. 5.1. Haff et al. 2016. Essentials of Strength… Human Kinetics 11  Neural Adaptations 12 Neuromuscular Junction Possible changes with anaerobic training include: increased surface area of the neuromuscular junction (NMJ) ◦more dispersed, irregularly shaped synapses and a greater total length of nerve terminal branching increased end-plate perimeter length and area, as well as greater dispersion of acetylcholine receptors within the end- plate region Fig. 5.1. Haff et al. 2016. Essentials of Strength… Human Kinetics 12  Neural Adaptations 13 Proprioceptor Adaptations Anaerobic training may enhance the stretch reflex response Enhances magnitude and rate of force development Muscles spindles & elasticity Shorter amortization Increase in the GTO threshold Decreases inhibitory impulses Fig. 3.9. Kenney et al. 2015. Physiology of Sport & Exercise. Hum.Kin. 13  Size Principle Adaptations 14 With heavy resistance training, all (Type 1 & 2) muscle fibers get larger because they are all recruited in consecutive order by their size to produce high levels of force (size principle) In advanced lifters, the central nervous system might adapt by allowing these athletes to recruit some motor units out of consecutive order. They can recruit larger ones first to help with greater production of power or speed in a movement (selective recruitment) in response to power or plyometric training. Fig. 5.2. Haff et al. 2016. Essentials of Strength… Human Kinetics Muscular Adaptations  Anaerobic Adaptations 16 Anaerobic training can lead to:  Muscle hypertrophy   strength & power   connective tissue strength (tendons & fascia)  Changes in muscle substrate content and glycolytic enzyme activity  Improved buffering capacity  Possible  in mitochondrial & capillary density  Fiber type shifts  Muscular Adaptations 17 Skeletal muscle adapts to anaerobic training primarily by increasing its size (cross-sectional diameter), facilitating fiber type transitions, and enhancing its biochemical and ultrastructural components. These changes result in enhanced muscular strength, power, and muscular endurance. Muscular Adaptations Terms 18 Hypertrophy  Muscularenlargement from an increase in the cross-sectional area (diameter not length) of the existing muscle fibers Transient vs. Chronic hypertrophy Hyperplasia  An increase in the number of muscle fibers via longitudinal fiber splitting  Questionable as to whether this happens in humans Atrophy  Decrease in muscle girth  Sarcopenia: age-related muscle atrophy  Muscular Hypertrophy 19 How do muscles hypertrophy? Increase in size of individual muscle fibers within the muscle 1) Sarcoplasmic Hypertrophy  amount of sarcoplasm & storage of substrates in it 2) Myofibrillar Hypertrophy 1.  size of myofibrils 2.  number of myofilaments (contractile proteins) and structural proteins ◦ Added to the external layer of the myofibril –  strength due to  sarcomeres in parallel 3.  number of myofibrils Splitting of existing myofibrils Different from hyperplasia Key Point 20 The process of hypertrophy involves both an increase in the synthesis of contractile proteins (actin and myosin) and structural proteins within the myofibril and an increase in the number of myofibrils within a muscle fiber. The new myofilaments are added to the external layers of the myofibril, resulting in an increase in its diameter.  Satellite Cells & Hypertrophy 21 Satellite cells are myogenic stem cells necessary for muscle regeneration 1) Acute damage or rapid stretching of a muscle promotes satellite cell activation & proliferation 2) Satellite cells migrate to the injured area to repair the myofiber 3) Satellite cells become new myonuclei  This is very important for muscle hypertrophy to maintain an adequate myonuclear domain. https://www.youtube.com/watch?v=lICMwXNpnLY Fig. 11.14. Kenney et al. 2022. Exercise Physiology… LWW  Muscular Adaptations 22 Structural and Architectural Changes  Resistance training increases myofibrillar volume, sarcoplasmic density, sarcoplasmic reticulum and T-tubule density, and sodium-potassium ATPase activity.  Sprint training enhances calcium release.  Resistance training increases angle of pennation. Other Muscular Adaptations  Reduced mitochondrial density  Decreased capillary density  Increased buffering capacity (acid-base balance)  Changes in muscle substrate content and enzyme activity Connective Tissue Adaptations  Connective Tissue Adaptations 24 Adaptations of Tendons, Ligaments, and Fascia  Theprimary stimulus for growth of tendons, ligaments, and fascia is the mechanical forces created during exercise. The degree of tissue adaptation is proportional to the intensity of exercise.  Consistent anaerobic exercise that exceeds the threshold of strain stimulates connective tissue changes. Fibroblasts create the primary structural component of all connective tissue: the collagen fiber  Type I for bone, tendon, and ligaments  Type II for cartilage Note that collagen fibers have a similar arrangement & striated appearance to muscle fibers. Fig. 5.5. Haff et al. 2016. Essentials of Strength… Human Kinetics  Connective Tissue Adaptations 25 Specific tendinous changes that contribute to size and strength increases include:  an increase in collagen fibril diameter  a greater number of covalent cross-links within the hypertrophied fiber  an increase in the number of collagen fibrils  an increase in the packing density of collagen fibrils Sites where connective tissues can increase strength and load-bearing capacity are:  at the junctions between the tendon (and ligament) and bone surface  within the body of the tendon or ligament  in the network of fascia within skeletal muscle  Connective Tissue Adaptations 26 General Bone Physiology  Trabecular bone (spongy) responds more rapidly to stimuli than does cortical bone (compact).  Minimal essential strain (MES) is the threshold stimulus that initiates new bone formation.  The MES is approximately 1/10 of the force required to fracture bone. Provides margin of safety against fracture Importance of progressive overload  Muscle strength and hypertrophy gains increase the force exerted on the bones, which may result in a corresponding increase in bone mineral density (BMD). Fig. 5.4. Haff et al. 2016. Essentials of Strength… Human Kinetics  Bone Remodeling 27  (a) Application of a longitudinal weight-bearing force causes the bone to bend (as depicted by the dotted line), creating a stimulus for new bone formation at the regions experiencing the greatest deformation. (b) Osteoblasts lay down additional collagen fibers along the periosteum. (c) Previously dormant osteoblasts migrate to the area experiencing the strain. (d) The collagen fibers become mineralized, and the bone diameter effectively increases. Fig. 5.4. Haff et al. 2016. Essentials of Strength… Human Kinetics  Why do we see specific adaptations?  Why do you see an increase in myofilament number?  Why is there an increase in myofibril and not myofiber number?  Why do we see an increase in tendon strength?  Why would you see a larger sarcoplasm?  Why can mitochondrial density go down?  What specific exercise stressors cause these adaptations? Tab. 22.5. McArdle et al. 2015. Exercise Physiology… LWW 29 Training Type → Adaptations 29 As the General Adaptation Syndrome states, the type of stressor (overload) will lead to specific adaptations in response to that specific stress. So what type of adaptations will be prioritized in response to the mechanical stress of high load resistance training? What type of adaptations will be prioritized in response to the metabolic stress and/or muscle damage stress of high volume / short rest? Reps Load Volume Rest Strength 85 Low 2-5min Hypertrophy 6-12 67-85 High 30-90sec  Review Questions 30 30 Explain the General Adaptation Syndrome and the importance of progressive overload in relation to a resistance training program Discuss the significance of neural adaptations in strength increases during a resistance training program  Explain how the reps & load of a “Strength” program increase these adaptations Explain at least 7 neural adaptations that were discussed 1 central, 2-3 MU, 2-3 NMJ, 2-3 proprioceptor Discuss many of the muscular adaptations that happen in response to anaerobic training Explain the underlying reasons for muscle fiber and thus muscle hypertrophy Figure & Notes References 31 Kenney, Wilmore, Costill. Physiology of Sport and Exercise (7th ed). Human Kinetics, 2018. McCardle, Katch, Katch. Exercise Physiology: Nutrition, Energy, and Human Performance, 8th Edition. Wolters Kluwer Health, 2014. Baechle & Earle. Essentials of Strength & Conditioning, 4th Edition. Human Kinetics, 2016. 31